Since the invention of PCR, numerous designs for thermocycling devices have been developed in an effort to increase the throughput, speed sensitivity and specificity of nucleic acid amplification. The trend over the past several years has focused on the development of miniaturized PCR apparatus and tests. Current designs for PCR microchips range from wide chambers of varying sizes and depths to narrow channels (linear or serpentine) and can have a single reaction chamber or arrays of chambers for multiple simultaneous reactions. See e.g., Krick and Wilding, Anal Bioanal Chem, 377:820-825 (2003). Some devices utilize a design format in which the reaction mixture is kept stationary and the temperature of the surrounding reaction chamber is cycled between the different temperatures, while other devices utilize a design format in which the reaction mixture is moved between different fixed temperature zones (e.g., a serpentine channel design; Krick and Wilding). These currently available thermocyclers utilize external electric thermal plates, infrared radiation, or heaters fabricated directly onto the surface of the devices (e.g., tungsten or platinum film) for directly heating and cooling of the PCR reaction mixture (Krick and Wilding).